Methylmercury hydroxide enhancement of translation and transcription of ovalbumin and conalbumin mRNA's

Nucleotide sequence of human rotavirus genome segment 10, an RNA encoding a glycosylated virus protein

The complete nucleotide sequence of human rotavirus (Wa strain) genome segment 10 was determined by using a cloned DNA copy. The sequence data indicated that segment 10 is A + T rich (65%) and consists of 750 base pairs. The positive strand of segment 10 contains a single open reading frame that extends 175 codons from the first AUG triplet (residues 42 through 44). The amino acid sequence of the segment 10 product was deduced from the nucleotide sequence. There are two distinct glycosylation sites at the N-terminal hydrophobic region, consistent with previous findings that this protein exists in a glycosylated form. The apparent molecular weight (20,000) of the unglycosylated, precursor polypeptide is in good agreement with the one calculated from the predicted amino acid sequence. Structural analysis of the positive strand (mRNA from segment 10) showed that it could form, like mRNA from segment 11, a stable panhandle structure involving the 5' and 3'-terminal regions. The nucleotide sequence of segment 10 from simian rotavirus, recently determined by Both et al. (J. Virol. 48:335-339, 1983) was found to be highly homologous to, and to share several important features with, segment 10 of human rotavirus.

Blocking of in vitro translation of Paramecium messenger RNAs is due to messenger RNA primary structure

Paramecium primaurelia mRNAs were translated in vitro in rabbit reticulocyte lysate and the products of translation were analyzed by their size. We show that the large majority of these products are of short but discrete sizes irrespective of the length of the mRNA which directs their synthesis. An illustrative example is given by the translation of mRNA of G surface antigen which directs the synthesis of a 50 kD polypeptide instead of the complete 250 kD protein. Control experiments suggest that the blocking is due to mRNA primary structure.

Identification of proopiomelanocortin neurones in rat hypothalamus by in situ cDNA-mRNA hybridization

Ardrenocorticotropic hormone (ACTH), beta-endorphin and the melanotropins (MSHs) are all derived from a single large precursor molecule, proopiomelanocortin (POMC) by individual processing through a series of co- and post-translational modifications. Although the primary site of synthesis is in the pituitary, POMC-derived peptides have been identified in various tissues, notably the brain (see refs 6, 7 for review). A major question concerning brain POMC is whether it is synthesized within the central nervous system (CNS) itself or whether it is taken up from plasma flowing in a retrograde fashion from the pituitary. POMC peptides have been detected immunohistochemically and biochemically in the medial basal hypothalamus, the amygdala and throughout the brain stem. POMC peptide-containing cell bodies have been identified only in two cell groups, however, principally in the periarcuate region of the hypothalamus and to a lesser extent in the nucleus of the tractus solitarius. These and other observations have suggested that POMC peptides are synthesized locally in the medial basal hypothalamus and reach other regions of the CNS by axonal transport. Civelli et al. identified POMC mRNAs in nucleic acid extracts of rat and bovine hypothalami by solution hybridization as well as Northern gel blot analysis, but because of the close proximity of the hypothalamus to the pituitary and the extremely low amounts of POMC mRNA being measured in the hypothalamus, the possibility of tissue contamination during dissection could not be ruled out. We report here the anatomical co-localization of POMC-related peptides and POMC-specific mRNAs to a single major cell group in the medial basal hypothalamus. The presence of POMC-specific mRNA in a POMC peptide-containing cell in the brain is strong support for POMC biosynthesis within brain tissue.

Developmental biochemistry of cottonseed embryogenesis and germination : XVI. Analysis of the principal cotton storage protein gene family with cloned cDNA probes

DNAs complementary to the mRNAs coding for the major cotton 48 kD and 52 kD storage proteins have been cloned and used to characterize the principal cotton storage protein gene family. The principal storage proteins are found to emanate from three subsets of genes that share some homology, as shown by common antigenic determinants shared by the proteins themselves, but that are distinguishable by nucleic acid hybridization. A single sequence subfamily of 2.26 kb mRNAs codes for the 69 kD preproteins (precursors to the mature 48 kD proteins) and two sequence subfamilies of 1.96 kb mRNAs each code for 60 kD preproproteins (precursors to the mature 52 kD proteins). Hybrid arrested translation shows that cloned members of these three subfamilies hybridize only with the mRNAs of a single subfamily at moderate criterion. These three subfamilies comprise all of the principal storage protein mRNAs detectable byin vitro translation. With hybridization at low criterion, some homology has been detected between the two 1.96 kb mRNA families, although no homology has yet been detected between the 2.26 kb mRNA family and either of the two 1.96 kb mRNA families.

Reverse transcriptase and its associated ribonuclease H: interplay of two enzyme activities controls the yield of single-stranded complementary deoxyribonucleic acid

The synthesis of single-stranded globin cDNA by the RNA-directed DNA polymerase activity of reverse transcriptase in the presence of oligothymidylate primers was investigated in order to determine the limitations to higher yields. The results indicated that the associated ribonuclease H activity, an integral part of reverse transcriptase, plays a large role in the synthesis of the first strand of cDNA and that the interplay of the two enzyme activities for any specific set of conditions determines the yield of single-stranded products. In both the presence and the absence of polymerization, the associated ribonuclease H catalyzed the deadenylation of mRNA, producing molecules that were somewhat shorter, highly homogeneous in size, and fully translatable into globin protein. They were also entirely lacking in the ability to serve as templates for cDNA synthesis. The reaction was completely dependent on oligothymidylate and completely independent of deoxyribonucleoside triphosphates. The initial rate of deadenylation was one-fourth the initial rate of initiation of polymerization when saturating levels of deoxyribonucleoside triphosphates were used in the polymerase reaction. In the presence of ribonuclease H activity, the DNA polymerase catalyzed the synthesis of an array of cDNAs including some that were full length. The initiation of polymerization was rate limiting: once synthesis had begun, it required 1-1.5 min to transcribe globin mRNA. However, most primers that were elongated were aborted prematurely. Maximum synthesis of full-length cDNA required stoichiometric levels of enzyme and high triphosphate levels, but regardless of conditions, the sum of completed cDNA and deadenylated mRNA accounted for only 50% of the input mRNA. The data fit a model in which synthesis of full-length cDNA molecules depends on the arrangement of primers and transcription initiation complexes on the poly(A) "tail" of mRNA.

Biochemical mapping of the simian rotavirus SA11 genome

Biochemical mapping experiments of the simian rotavirus SA11 genome were performed to determine which double-stranded RNA segment coded for each of the viral polypeptides. Viral RNA transcripts were synthesized in vitro by using the endogenous viral RNA polymerase and fractionated by electrophoresis in acid-urea agarose gels. The fractionated transcripts were translated in two cell-free systems: micrococcal nuclease-treated reticulocyte lysates and wheat germ extracts. The polypeptide products were identified by polyacrylamide gel electrophoresis and partial peptide analysis and compared with polypeptides synthesized in infected cells or found in purified virus. The RNA segment that coded for each transcript was determined by hybridization of the fractionated transcripts to the double-stranded RNA genome and analysis of the hybrids by electrophoresis in polyacrylamide gels. Primary gene products were assigned for 10 of the rotavirus transcripts and 10 of the double-stranded RNA segments. The coding assignments are as follows: the inner-capsid polypeptides, VP1, VP2, and VP6, were assigned to segments 1, 2, and 6, respectively; the major outer-capsid polypeptides, VP3 and VP7, were assigned to segments 4 and 9, respectively; segments 5, 7, and 8 coded for nonstructural polypeptides with molecular weights of 53,000, 34,000, and 35,000, respectively; segment 10 coded for the 20,000-molecular-weight precursor to the 29,000-molecular-weight glycosylated nonstructural polypeptide; and segment 11 coded for a 26,000-molecular-weight polypeptide that may be the precursor to the minor outer-capsid polypeptide VP9. Several methods were used to determine the product of gene segment 3, and the problems associated with the identification of this gene product are discussed.

Synthesis of vimentin in a reticulocyte cell-free system programmed by poly(A)-rich RNA from several cell lines and rat liver

Poly(A)-rich RNA has been isolated from Ehrlich ascites tumor (EAT) cells and translated in a rabbit reticulocyte cell-free system. The intermediate filament protein, vimentin, was found to be a major translation product. Fractionation of the poly(A)-rich RNA by sucrose gradient centrifugation showed that the vimentin mRNA had a sedimentation coefficient of about 18 S corresponding to a molecular size of about 2000 nucleotides. This means that it must possess significant non-coding regions. Vimentin synthesized in vitro was identical to native vimentin with regard to its precipitability with ammonium sulphate, extent of phosphorylation and susceptibility to digestion by the vimentin-specific, Ca2+-activated proteinase. Poly(A)-rich RNA was also isolated from a number of tissue-culture cells and rat liver, which contain varying amounts of vimentin in situ. It was found that the amount of vimentin synthesized by these RNA preparations in a rabbit reticulocyte cell-free system is proportional to the amount of vimentin detectable in situ, suggesting that the amount of cellular vimentin may be controlled at the level of transcription.

Characteristics of antibodies to guinea pig (Na+ + K+)-adenosine triphosphatase and their use in cell-free synthesis studies

Antibodies have been produced, in three rabbits, to Na/K-ATPase purified from guinea pig renal outer medulla. Each rabbit produced antibodies to both the alpha (catalytic) and the beta (glycoprotein) subunits of Na/K-ATPase. The titers of the anti-alpha and anti-beta antibodies varied with time and between rabbits. None of the antisera inhibited Na/K-ATPase activity under various preincubation conditions. A method is presented for separating small amounts of anti-alpha subunit from anti-beta subunit antibodies. There was no cross-reactivity of antibodies to one subunit with the other subunit. The alpha subunit of the Na/K-ATPase was cleaved into a 41,000-dalton peptide (that contains the ATP phosphorylating site) and a 58,000-dalton hydrophobic peptide as described by Castro and Farley (Castro, J., Farley, R.A., 1979, J. Biol. Chem. 254: 2221-2228). Anti-alpha antibodies from all of the rabbits reacted with both proteolytic fragments. The anti-guinea pig Na/K-ATPase antisera (pooled) cross-reacted with the alpha subunit of Na/K-ATPase from human, cow, dog, rabbit, rat, mouse, turtle, and toad; and with the beta subunit from human, rat, and mouse. The loci of cross-reactivity were investigated using partially purified canine kidney Na/K-ATPase cleaved with trypsin as described above. The anti-sera from rabbits 1 and 2 cross-reacted with the 41,000-dalton peptide from the dog but very little with the 58,000-dalton peptide. No cross-reactivity was observed with antiserum from rabbit 3 to either fragment. Guinea pig kidney RNA was translated in a rabbit reticulocyte lysate system followed by immunoprecipitation with the antisera. The molecular weight of the cell-free synthesized alpha chain was 96,000 daltons. Its identity was established with purified anti-alpha antibodies and by immunocompetition with purified Na/K-ATPase and Ca-ATPase. Translation of the beta subunit was not detected in this system.

Partial purification of the messenger RNA for eukaryotic elongation factor Tu from Artemia salina

Polyadenylated RNA from developing Artemia salina cysts was fractionated by centrifugation through a sucrose gradient containing methylmercuric hydroxide (CH3HgOH). Aliquots of each fraction were directly added to a rabbit reticulocyte lysate to program protein synthesis in vitro. The translation products were assayed for eukaryotic elongation factor Tu (eEF-Tu) by immunoprecipitation with an antibody raised in rabbits and purified by affinity chromatography. The immunoprecipitated radioactivity was analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate. Sequences coding for eEF-Tu sediment in the 20-S region of the gradient and form a major component of the poly(A)-containing RNA. The mRNA of the 20-S region, comprising about 10% of the poly(a)-containing RNA fractionated on the gradient, has been translated in vitro and 30% of the translation products represent immunoprecipitable eEF-Tu protein chains with an Mr of 50000.

Cloning of four DNA fragments complementary to human thyroglobulin messenger RNA

Human thyroglobulin mRNA was isolated from Graves' goitres by size selection of total poly(A)-rich RNA in a sucrose gradient. It sedimented at 33 S, as in other mammalian species, and showed a single component of approximately 8500 bases by gel electrophoresis. cDNA was synthesized from the 33-S RNA by using reverse transcriptase in the presence of human placenta ribonuclease inhibitor and in conditions allowing the formation of long transcripts. The latter was made double-stranded using reverse transcriptase and blunt-ended with nuclease S1. After tailing with dCTP and terminal transferase, the double-stranded cDNA was annealed to pBR322 DNA that had been cleaved at the endonuclease PstI site and tailed with dGTP. The resulting plasmids were used to transform Escherichia coli C600 cells and four cloned recombinants were selected. Each plasmid DNA was shown to contain a sequence complementary to human thyroglobulin mRNA by hybridization with a labeled 33-S mRNA, visualization of cDNA . mRNA hybrids by electron microscopy and filter hybridization selection of mRNA directing the synthesis of immunologically related thyroglobulin peptides in the reticulocyte lysate. The four inserted DNA sequences were 1400 - 1800 base pairs long, two of them showing an homologous sequence of 1100 base pairs. Together, the four cloned DNA fragments represented 63% of the 8500 bases of human thyroglobulin mRNA.

Heavy chain variable region contribution to the NPb family of antibodies: somatic mutation evident in a gamma 2a variable region

To examine germ line genes of the heavy chain variable region (VH) that might contribute to formation of antibodies of the NPb family, we have derived cDNA clones from two hybridomas making NPb antibodies. One, B1-8, made an IgM protein and was derived during a primary response; the other, S43, made an IgG2a protein and was derived during a hyperimmune response. Sequence comparison of the two clones showed that they differed by only 10 bp in the VH region, had very different D segments and had identical J segments (J2). A set of closely related germ line VH genes was then cloned from a partial Eco RI library of C57Bl/6 DNA. By comparing the germ line VH regions to the cDNA VH regions, we identified seven potential candidates for encoding the VH regions of NPb antibodies. The seven VH regions were sequenced, and one V(186-2) contained exactly the DNA sequence found in the clone derived from B1-8. None of the DNA sequence differences that distinguished the S43-derived clone from the B1-8 clone was found in any of the other six germ line genes. Because the S43 sequence was more closely related to the V(186-2) germ line sequence than to any of the other VH genes, we conclude that the differences between the genes resulted from somatic mutation and that the two hybridomas derived their VH regions from the same germ line gene. Certain of the sequenced VH genes contain crippling mutations; the repertoire of germ line VH genes that can contribute to the diversity of antibodies may therefore be less than the total number of genes detectable by hydridization.

Evidence for messenger ribonucleic acid of an ammonium-inducible glutamate dehydrogenase and synthesis, covalent modification, and degradation of enzyme subunits in uninduced Chlorella sorokiniana cells

The cells of Chlorella sorokiniana cultured in nitrate medium contain no detectable catalytic activity of an ammonium-inducible nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase (NADP-GDH). However, several lines of experimental evidence indicated that the NADP-GDH messenger ribonucleic acid was present at high levels and was being translated in uninduced cells. First, binding studies with 125I-labeled anti-NADP-GDH immunoglobulin G and total polysomes isolated from uninduced and induced cells showed that NADP-GDH subunits were being synthesized on polysomes from both types of cells. Second, when polyadenylic acid-containing ribonucleic acid was extracted from polysomes from uninduced and induced cells and placed into a messenger ribonucleic acid-dependent in vitro translation system, NADP-GDH subunits were synthesized from the ribonucleic acid from both sources. Third, when ammonia was added to uninduced cells, NADP-GDH antigen accumulated without an apparent induction lag. Fourth, by use of a specific immunoprecipitation procedure coupled to pulse-chase studies with [35S]sulfate, it was shown that the NADP-GDH subunits are rapidly synthesized, covalently modified, and then degraded in uninduced cells.

Translation in vivo and in vitro of mRNAs coding for vitellogenin, serum albumin and very-low-density lipoprotein II from chicken liver. A difference in translational efficiency

Characterisation of polysomes from estrogenized chicken liver revealed that very-low-density lipoprotein II (VLDLII), serum albumin and vitellogenin mRNAs are differently packed with ribosomes during translation in vivo. Tne ribosome density per number of nucleotides is high for VLDLII mRNA, intermediate for serum albumin mRNA and low for vitellogenin mRNA. This difference in ribosomal load is maintained throughout the period of hormone effect. The differential utilisation observed for vitellogenin and VLDLII mRNAs partly explains the large difference in molar production rate between these yolk protein precursors. Translation properties and efficiency of the three hepatic mRNAs were also compared in the mRNA-depleted reticulocyte lysate. Elongation of the nascent chains for vitellogenin and serum albumin proceeded in a discontinuous fashion. Initiation in vitro was studied at varying ionic strengths, in the presence of aurintricarboxylic acid, and at suboptimal hemin concentrations. VLDLII mRNA expression is by far the most resistant to 7-methylguanosine 5'-triphosphate (m7GTP) and high salt concentrations, vitellogenin mRNA the least. This behaviour resembles the differential utilisation of the mRNAs in vivo. The putative structural basis of these differences is discussed.

Expression of J chain RNA in cell lines representing different stages of B lymphocyte differentiation

During B cell differentiation to pentamer IgM secretion, synthesis of the pentamer joining component, the J chain, is initiated. We investigated the mechanism for initiating J chain synthesis by analyzing murine cell lines representing different stages in B cell differentiation. The expression of functional J chain mRNA was evaluated by cell-free translation and specific immunoprecipitation of a J chain product. The expression of precursor mRNA was examined by hybridization with a J chain probe obtained by molecular cloning of cDNA. No J chain-specific RNA could be demonstrated in a lymphoma line representative of an undifferentiated B lymphocyte, but three species of J chain RNA were identified in hybrid cell lines representative of IgM-secreting plasma cells: a mature message of approximately 1.5 kb and two minor components of 2.5 and 0.92 kb. The encounter of a B cell with antigen or mitogen must therefore trigger events that effect either transcription of J chain sequences or their intranuclear stabilization.

The ovalbumin gene family: hormonal control of X and Y gene transcription and mRNA accumulation

The ovalbumin gene family is composed of three genes, X, Y and ovalbumin, which are expressed in laying hen oviduct. We have analyzed the in vivo transcription products of X and Y genes and the effect of steroid hormones on their synthesis and accumulation. As in the case of ovalbumin, the complete gene transcripts and processing intermediates are present in the poly(A)+ RNA fraction. The mature RNAs are found in polysomes and are translated into proteins. The expression of X and Y genes is controlled by steroid hormones: X and Y RNAs are not detectable in oviducts from chicks withdrawn from estrogen stimulation, whereas in chicks stimulated with estrogen for 7 days, X RNA represents 0.3% and Y RNA 0.8% of ovalbumin mRNA. In laying hen, however, the levels of X and Y RNAs are about 2% of ovalbumin mRNA. After stimulation with other steroid hormones, alone or in combination, the level of X and Y RNA does not achieve that detected in laying hen. Progesterone has a much weaker effect on X RNA accumulation than on that of Y and ovalbumin mRNAs. Studies with isolated nuclei show that X and Y gene expression is regulated by hormones at the level of transcription. However, the differences observed between the transcription rates and the accumulation of X and Y mRNAs suggest that the expression of X and Y genes could also be controlled at the levels of RNA processing and/or mRNA stability.

Developmental regulation of laccase levels in Aspergillus nidulans

Asexual spores (conidia) of Aspergillus nidulans contain a dark green pigment which is not present in other cell types. Synthesis of this pigment is catalyzed, in part, by a developmentally controlled p-diphenol oxidase, or laccase, encoded at the gamma A genetic locus (A. J. Clutterbuck, J. Gen. Microbiol. 70:423-435, 1972). We have investigated the mechanisms regulating expression of the gamma A gene of A. nidulans. Vegetative hyphae grown in submerged culture lacked detectable laccase enzyme activity and neither contained nor synthesized immunoprecipitable laccase protein. When such cultures were induced to conidiate by harvesting the cells onto filter papers and aerating them, laccase levels began to increase after 10 to 16 h, reached a peak at 20 to 36 h, and then declined slowly. Immunological assays showed that increases in laccase enzyme activity were (i) proceded by a transient rise in the relative rate of laccase protein synthesis and (ii) closely paralleled by increases in the amount of laccase protein. Addition of cycloheximide to cultures at any time after inducing conidiation inhibited further accumulation of laccase enzyme activity. These data are most consistent with increases in laccase levels being due to regulated, de novo synthesis of laccase protein. Addition of inhibitors of ribonucleic acid synthesis to conidiating cultures also inhibited further accumulation of laccase, suggesting that laccase expression is regulated by alterations in the transcriptional activity of the gamma A locus.

Improvements in immunoprecipitation of specific messenger RNA. Isolation of highly purified conalbumin mRNA in high yield

We have described previously procedures for the isolation of specific mRNA employing immunoprecipitation of polysomes. In spite of our success with ovalbumin mRNA in the chicken oviduct, we have had considerable difficulties in applying these same published techniques to the immunopurification of conalbumin mRNA, despite the fact that the chicken oviduct synthesizes up to 10% of protein as conalbumin. Here we describe a number of modifications and refinements which have proved essential in obtaining intact conalbumin mRNA in high purity and high yields. These refinements include: (a) improved purification of conalbumin in order to remove contaminating proteins that result in impure antibodies; (b) improved isolation of specific conalbumin antibody in high yields; (c) improved methods for reducing contamination by non-specific polysomes; (d) improved techniques for isolation of RNA from immunoprecipitates resulting in less degradation and higher recovery of conalbumin mRNA; (E) improved techniques for efficient translation of conalbumin mRNA involving treatment of the RNA with methylmercury prior to translation. We conclude that problems involved in the immunoprecipitation of different mRNAs may differ, and that various refinements in techniques may be required for obtaining highly purified preparations of intact mRNA in high yields.